A conventional technology is described referring to FIGS. 20–22.
FIG. 20 is a cross sectional view of a conventional loudspeaker, FIG. 21 is a cross sectional view in part of a portable telephone unit showing a state where the loudspeaker is mounted therein.
Referring to FIG. 20, a magnetized magnet 1 is sandwiched by an upper plate 2 and a yoke 3 to form a magnetic circuit 4, and a frame 6 is connected to the yoke 3 of magnetic circuit 4. A diaphragm 7 coupled with a voice coil 8 is adhered and fixed on the circumference of frame 6 so that the voice coil 8 is inserted in a magnetic gap 5 of magnetic circuit 4.
FIGS. 21 and 22, respectively, show a state where a conventional loudspeaker 10 is mounted in a portable telephone unit. A display device 12 is disposed in the outer case 11 of portable telephone unit, and a loudspeaker 10 is disposed on a reverse surface of an outer case, or a surface opposite to the display device 12. An operation section 13 is disposed besides the display device 12. Furthermore, a receiver 14 is provided next to the display device 12.
In the recent requirements towards small-sized and multi-functioning of the portable telephone units and other electronic appliances, the loudspeaker 10 is also requested to be still more downsized, and to have a greater freedom in the mounting disposition. It is essential to make an area of the diaphragm 7 smaller if a loudspeaker 10 is to be downsized; however, a diaphragm 7 having a reduced area accompanies a problem of reduced sound pressure level.
Among the compact-sized portable telephone units, some are further requested to be compatible with stereo-phonic signals; then a telephone unit needs to be mounted with a plurality of loudspeakers 10. In such a case, the loudspeaker 10 is requested to become more compact.
The present invention addresses to provide a loudspeaker that contributes to a further downsizing of the electronic apparatus such as a portable telephone units and the like.